JP2927957B2 - Phenylcyclohexanes and liquid crystal media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a compound of formula I (Where Hal is F or Cl, l is 1, 2 or 3, r is 0 or 1 to 6, and E is -A-, -A-CH
₂ CH ₂ — or —CH ₂ CH ₂ —A—, where A is trans-1,
4-cyclohexylene, 1,4-phenylene, 3-fluoro-1,4-phenylene, 3,5-difluoro-1,4-phenylene or a single bond, Q is -CF _2, -OCF _2, -CF ₂ CF ₂
-, - OCF ₂ CF ₂ - or a single bond, Y is H, F or Cl, and relates to novel phenyl cyclohexanes of X and Z is H or F independently of each other).

EP-A 0 330 216 has the formula F ₂ C = CH (CH ₂ ) _n − (n = 0 to 2
Disclosed is a liquid crystal having a group (0). However,
The compound described therein is a liquid crystal having a high positive dielectric anisotropy having a nitrile group.

However, such compounds do not meet the high requirements for electrical resistance, such as those required for displays with an active matrix. further,
Such compounds have a rather high temperature dependence of the threshold voltage and a significantly lower clearing point due to benzonitrile.

Similar to analogous compounds, for example those known from DE-A 26 36 684, the compounds of the formula I can be used as liquid-crystalline medium components for displays, in particular based on the principle of twisted cells.

All the materials used hitherto for this purpose have certain disadvantages, such as very high melting points, very low clearing points,
It has very poor stability to the action of heat, light or electric fields, very low electrical resistance, inadequate elasticity, or a very high temperature dependence of the threshold voltage.

The materials used hitherto are disadvantageous, especially in super-twisted (STN) displays with a twist angle significantly larger than 220 ° or in displays with an active matrix.

In particular, it is an object of the present invention to find a novel liquid crystal compound which is suitable as a liquid crystal medium component for a nematic medium having a positive dielectric anisotropy and has no disadvantage of a known compound or has only a very small amount. Is the purpose. This object has been achieved by providing new compounds of the formula I.

It has been found that the compounds of the formula I are particularly suitable as liquid-crystalline medium components. In particular, using these compounds, a wide nematic range, excellent nematic formability up to low temperatures, excellent chemical stability, excellent elasticity, remarkable ε⊥ in positive dielectric anisotropy, low threshold voltage A liquid crystal medium having temperature dependency and / or low optical anisotropy can be obtained. In addition, these new compounds have a high positive dielectric anisotropy as well as good solubility and favorable viscosity in other components of this type of medium.

The compounds of the formula I make it possible to produce both STN displays with very sharp electro-optical characteristic curves and active matrix displays with excellent long-term stability. By properly choosing r and n, the threshold voltage in both types of displays can be significantly reduced.

In pure state, the compounds of the formula I are colorless and form liquid-crystalline mesophases in the temperature range preferred for electro-optical use.

The invention therefore relates to the compounds of the formula I and to the use of the compounds of the formula I as liquid-crystalline medium components, to liquid-crystalline media containing at least one compound of the formula I and to electro-optical displays containing such media.

Above and below, r, l, E, A, X,
Q, Y and Z have the above meanings unless otherwise stated.

When QY is F, Z and / or X is preferably F.

In the compounds of the formula I, the alkylene group (CH ₂ ) _r is preferably straight-chain. Thus, preferably, the groups are methene, ethylene, n-propylene, n-butylene, n-pentylene or n-hexylene. r
Is preferably 2 or 4, and more preferably 3 or 5. Furthermore, especially when l is 1, r
Is preferably 0.

It is preferred that

Q is _{-OCF 2 CF 2 -, - OCF} 2 - or is preferably a single bond.

 Y is preferably H or F.

Especially preferred Q-Y is, F, Cl, -OCF _3, a -OCF ₂ H or -OCF ₂ CF ₂ H.

Hal is preferably F or, if l = 1, Cl.

In addition, compounds of formula I are described in the literature [eg Houben-Weyl, published by Georg-Thieme publisher, Stuttgart, "Methoden der Organischen Chemie". The basic reaction is carried out in a manner known per se, in particular, as described in the above reaction and under suitable reaction conditions. Similarly, unconventional methods, known per se but not described in further detail here, can also be used.

The starting materials can also be formed therein, if desired, without further isolation of the starting materials from the reaction mixture, directly so as to obtain the compounds of the formula I.

Precursors suitable for synthesizing compounds of the present invention can be obtained, for example, according to the following synthetic scheme.

Scheme 1: Higher homologs can be obtained by repeating these series of reactions in the same manner.

The Grignard compound obtained from the corresponding bromobenzene derivative is reacted with chlorotrialkyl orthotitanate or chlorotrialkyl orthozirconate by the method of WO 87/05599 to obtain tertiary cyclohexanol. Dehydration, hydrogenation of the double bond and isomerization are carried out according to the usual methods to obtain the trans-cyclohexanecarboxylic acid ester. Aldehydes suitable for the compounds according to the invention are obtained from the latter compounds by customary standard methods. The compounds of the present invention can be obtained from these aldehydes by Wittig synthesis and subsequent hydrogenation of the double bond.

The bromobenzene derivatives used as starting materials are in part known and can be prepared from compounds known in the literature in part by standard methods of organic chemistry without particular difficulty. For example, OCF ₃ -, or OCHF ₂ - compound from the corresponding phenols and CF ₃ -, or CN- compounds can be obtained from the corresponding benzoic acids. formula And corresponding monofluorinated compounds can be obtained, for example, from known precursors where QY is H by lithiation at low temperature followed by reaction with a suitable electrophile.

The homologation shown in the above reaction scheme can also be performed by other standard methods known to those skilled in the art.

Formula I wherein E is 1,4-phenylene, 3-fluoro-1,4-phenylene or 3,5-difluoro-1,4-phenylene
Can be produced according to the above synthesis scheme. At this time, the coupling reaction [E.
Petsch, Kontakte (Darmstadt), 1988 (2)), page 15] Can be used in place of the substituted bromobenzene derivative.

The following scheme illustrates the synthesis of precursors suitable for preparing compounds where E is trans-1,4-cyclohexylene.

Scheme 2: Higher aldehydes, carboxylic acids and phosphonium salts can be prepared as shown in Scheme 1. It is clear to a person skilled in the art that dehydration of the cyclohexene intermediate (for example with chloranil) can also give compounds according to Scheme 2 in which E is 1,4-phenylene.

By the way, the compounds of the formula I are obtained by the Wittig method and the subsequent hydrogenation by ω-fluoro-, ω-chloro-,
Difluoro- or ω-trifluoro- or ω-dichloro or ω-trichloro-n-alkanals have the formula Can be obtained by a method known per se by reacting with the above-mentioned phosphonium salt. Here, the types of the ω-haloalkanal and r are selected according to the desired end product.

However, conversely, it is also possible to react the above-mentioned aldehydes with the phosphonium salts of ω-fluoro-, ω-chloro-, ω-difluoro- or ω-trifluoroalkylhalogen compounds by the Wittig method. Similarly, compounds of formula I can be easily obtained by causing by reacting with a fluorinating agent of DAST like the above aldehydes, or carboxylic acids mentioned above to react with SF _4. Particularly highly preferred synthetic methods are shown schematically below.

_{CF 3 - (CH 2) x} -CHO _{and, CF 3 - (CH 2)} x -Hal and,
CHF _2- (CH ₂ ) _x -Hal (Hal = Br or I; x = 1, 2 or 3)
Corresponding starting materials are known to those skilled in the art and have been described in the literature.

Similarly, compounds of formula I where l = 1 are readily obtained by reacting the above aldehydes with a halogenating agent such as thionyl chloride or tetraalkylammonium fluoride. Particularly highly preferred synthetic methods are shown schematically below.

Hal- (CH _{2) x} -CHO and _{F- (CH 2) x -Hal (} Hal = Br or I; x = 1, 2 or 3) corresponding starting materials such as are known to those skilled in the art and literature It is described in.

The liquid crystal medium of the present invention preferably contains 2 to 40, especially 4 to 30 components as further components in addition to one or more compounds of the present invention. It is particularly preferred that these media contain 7 to 25 components besides one or more compounds of the present invention. These further components are nematic or nematic phase-forming (mono- or isotropic) substances, in particular biphenyls, terphenyls, phenyl benzoates or cyclohexyl benzoates, phenyl or cyclohexyl esters of cyclohexanecarboxylic acid. Phenyl or cyclohexyl esters of cyclohexyl benzoic acid, phenyl or cyclohexyl esters of cyclohexyl cyclohexane carboxylic acid, cyclohexyl phenyl esters of benzoic acid, cyclohexyl phenyl esters of cyclohexane carboxylic acid and cyclohexyl phenyl esters of cyclohexyl cyclohexane carboxylic acid, Phenylcyclohexanes, cyclohexylbiphenyls, phenylcyclohexylcyclohexanes, cyclohexyl Rohekisan acids, cyclohexyl cyclohexenes, cyclohexyl cyclohexyl cyclohexenes, 1,4-bis - cyclohexyl benzene, 4,4-bis - cyclohexyl biphenyls,
Phenylpyrimidines or cyclohexylpyrimidines, phenylpyridines or cyclohexylpyrimidines, phenyldioxane or cyclohexyldioxane, phenyl-1,3-dithiane or cyclohexyl-1,3-dithiane, 1,2-diphenylethanes,
1,2-dicyclohexylethanes, 1-phenyl-2-
Cyclohexylethanes, 1-cyclohexyl-2-
(4-phenyl-cyclohexyl) ethanes, 1-cyclohexyl-2-biphenylethanes, 1-phenyl-
Preferably, it is selected from the group consisting of 2-cyclohexyl-phenylethanes and tolanes.

The 1,4-phenylene groups in these compounds may be fluorinated.

The characteristics of the most important compounds suitable as additional components of the medium of the present invention can be shown by the following formulas 1, 2, 3, 4 and 5.

R'-L-E-R " 1 R'-L-COO-E-R" 2 R'-L-OOC-E-R "3 R'-L-CH 2 CH 2 -E-R" 4 R '-L-CC-ER "5 L and E, which may be the same or different in formulas 1, 2, 3, 4 and 5, are in each case independently of one another -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-,
-Cyc-Cyc-, -Pyr-, -Dio-, -G-Phe- and -G-Cyc- and enantiomers thereof, wherein Phe is unsubstituted or fluorine-substituted 1,4-phenylene; Cyc is trans-1,4-cyclohexylene or 1,4-cyclohexenylene, Pyr is pyrimidine-2,5-diyl or pyridine-2,5-diyl, and Dio is 1,3-dioxane-2. , 5-diyl and G is 2- (trans-1,4
-Cyclohexyl) ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or 1,3-dioxane-
2,5-diyl].

Preferably one of the groups L and E is Cyc, Phe or Pyr. E is preferably Cyc, Phe or Phe-Cyc. The liquid crystal medium of the present invention comprises one or more components selected from compounds of formulas 1, 2, 3, 4 and 5 wherein L and E are selected from the group consisting of Cyc, Phe and Pyr, And E is selected from the group consisting of Cyc, Phe and Pyr, and the other group is -Phe-Phe-, -Phe-Cyc
-, -Cyc-Cyc-, -G-Phe- and -G-Cyc- further comprising one or more components selected from compounds of formulas 1, 2, 3, 4 and 5 selected from the group consisting of: And, in addition to these, if necessary, groups L and E are -Phe-Cyc-,
It preferably comprises one or more components selected from compounds of formulas 1, 2, 3, 4 and 5 selected from the group consisting of -Cyc-Cyc-, -G-Phe- and -G-Cyc-. .

In formulas 1, 2, 3, 4 and 5, R ′ and R ″ are each independently of the other alkyl having up to 8 carbon atoms,
When it is alkenyl, alkoxy, alkenyloxy or alkanoyloxy, the lower formulas 1a, 2a,
Called 3a, 4a and 5a.

In the formulas 1, 2, 3, 4 and 5, R ′ is the lower formula 1a
Has the same meaning as in the case of 5a, wherein R "is -CN, -CF ₃ ,
Cases of —OCF ₃ , F, Cl or —NCS are referred to as lower formulas 1b, 2b, 3b, 4b, and 5b, respectively.

In the sub-formulas 1a to 5a, most of these compounds differ in R 'and R ", and one of these groups is usually alkyl or alkenyl.

In formulas 1b to 5b, R 'is preferably alkyl or alkenyl. R "is -F, Cl, CF ₃ and -OCF ₃
Preferably, the group consisting of However, other variants of the proposed substituents in the compounds of formulas 1, 2, 3, 4 and 5 are also well known. Many such substances or mixtures thereof are also commercially available. All these substances can be obtained by methods known in the literature or methods analogous thereto.

In addition to the components from Group 1 consisting of compounds 1a, 2a, 3a, 4a and 5a, the vehicle according to the invention comprises compounds 1b, 2b, 3b, 4b and 5b
Also preferably comprises components from the group consisting of (group 2), the proportions of these components being: group 1: 20-90%, especially 30-90% group 2: 10-80% In particular 10 to 50% The sum of the proportions of the compounds of the invention and of the compounds from groups 1 and 2 amounts to 100%.

The medium according to the invention preferably contains 1 to 40%, in particular 5 to 30%, of a compound according to the invention. Even more preferred are media containing more than 40%, especially 45-90% of the compound of the invention. The medium preferably contains 3, 4 or 5 compounds according to the invention.

The medium according to the invention is produced in a manner customary per se. In general, these components dissolve each other particularly well at elevated temperatures. The liquid crystal phase can be modified with suitable additives according to the invention for use in all types of liquid crystal display elements disclosed thus far. Additives of this kind are known to the person skilled in the art and are described in the literature [Liquid crystal handbook (H. Kelker / R. Hatz)
and book of Liquid Crystals), Chemical Publishers, Weinheim, 1980]. For example, polychromatic dyes can be added to produce a colored guest-host system, and certain substances can be added to adjust the dielectric anisotropy, viscosity and / or orientation of the nematic phase.

The following examples illustrate, but do not limit, the invention. mp. = melting point, cp. = clearing point.
Above and below, percentages are by weight,
All temperatures are in ° C. By "normal operation" is meant that water is added, the mixture is extracted with methylene chloride, the organic phase is separated off, dried and evaporated, and the product is purified by crystallization and / or chromatography.

Furthermore, the abbreviations have the following meanings: C: crystalline solid state, S: smectic phase (representation of the type of smectic phase), N: nematic state, Ch: cholesteric phase, I: isotropic phase. The number between these two symbols is ° C
Shows the indicated conversion temperature.

DAST Diethylaminosulfur trifluoride DCC Dicyclohexylcarbodiimide DDQ Dichlorodicyanobenzoquinone DIBALH Diisobutylaluminum hydride DMSO Dimethylsulfoxide POT Potassium tert-butanolate THF Tetrahydrofuran pTSOH p-Toluenesulfonic acid In the following examples, the substituent Z in each case is Q
It is in the position ortho to -Y.

Example 1 Potassium tert-butyrate solution in THF
Add dropwise to a suspension of 0.2 m of the phosphonium salt in 500 ml of THF at 5 ° C. to give an orange ylide suspension. In this suspension,
Pass trifluoroacetaldehyde gas at 0-5 ° C until the suspension is colorless. An extraction operation and filtration through silica gel are performed to obtain an alkene (cis-trans mixture). This is dissolved in ethanol and hydrogenated after addition of the PtO ₂ catalyst to give the product.

The following compounds of formula I (E = single bond, Hal = F, l =
3) is obtained in exactly the same way or according to the synthetic scheme described above.

Similarly, compounds of formula I E = single bond, Hal = F and 1 =
Get 2.

Example 2 Heat 0.1 m carboxylic acid with 0.4 m SF ₄ in an autoclave at 130 ° C. for 10 hours. An extraction operation, followed by chromatographic purification and crystallization, gives the product from the crude mixture.

The following compounds of formula I (E = 1,4-phenylene, Hal =
F, l = 3) are obtained in exactly the same way or according to the synthesis scheme described above.

Similarly, the following compounds of formula I (E = 3-fluoro-1,1,
4-phenylene, Hal = F, l = 3) is obtained.

Similarly, the following compounds of formula I are obtained (E = 1,4-phenylene, Hal = F, l = 2).

Similarly, the following compounds of the formula I are obtained (E = 3,5-difluoro-1,4-phenylene, Hal = F, 1 = 2).

Example 3 Dissolve 0.02 m of this aldehyde compound in 50 ml of THF,
A further 0.05 m of DAST is added. This liquid is stirred at room temperature for 24 hours, and the product is isolated by performing an extraction operation, followed by purification by chromatography.

The following compounds of the formula I (E = trans-1,4-cyclohexylene, Hal = F, 1 = 2) are obtained analogously or according to the above synthesis scheme.

Similarly, the following compounds of formula I are obtained (E = trans-1,4-cyclohexylene, Hal = F, 1 = 3).

Example 4 A mixture of 0.1 m of the above alcohol, 0.11 m of mesylate and 0.3 m of tetrabutylammonium fluoride in 300 ml of acetonitrile is refluxed for 4 hours. The crude product is purified by evaporation and extraction operations, which are purified by chromatography.

The following compounds of formula I (E = single bond, l = 1, Hal =
F) is obtained in exactly the same way or according to the synthesis scheme described above.

Similarly, compounds of the formula I are obtained in which E = single bond, 1 = 1 and Hal = Cl.

Example 5 A mixture of 0.05 m of this alcohol compound and 0.1 m of thionyl chloride is refluxed for 6 hours and operated as in Example 4.

The following compounds of formula I (E = 1,4-phenylene, 1 =
1, Hal = Cl) in exactly the same way or according to the above synthesis scheme.

Similarly, the following compounds of formula I (E = 3-fluoro-1,1,
4-phenylene, l = 1, Hal = Cl).

Similarly, the following compounds of the formula I are obtained (E = 1,4-phenylene, 1 = 1, Hal = F).

Similarly, the following compounds of formula I (E = 3-fluoro-1,1,
4-phenylene, l = 1, Hal = F) is obtained.

Similarly, the following compounds of the formula I are obtained (E = 3,5-difluoro-1,4-phenylene, 1 = 1, Hal = F).

Example 6 The desired product is obtained using the above alcohol in the same manner as in Example 4.

The following compounds of the formula I (E = trans-1,4-cyclohexylene, 1 = 1, Hal = F) are obtained analogously or according to the above synthesis scheme.

Similarly, the following compounds of formula I (E = trans-1,4
-Cyclohexylene, l = 1, Hal = Cl).

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Prague, Herbert Germany 6100 Darmstadt Wingersbergstrasse 5 (72) Inventor Rieger, Bernhard 2834 Otadaira, Nara-machi, Midori-ku, Yokohama-shi, Kanagawa Prefecture Wacore Tamagawa Gakuen (56) References JP-A-63-185936 (JP, A) JP-A-60-84232 (JP, A) Table 1-503145 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C07C 22 / 04,25 / 18,43 / 225 C09K 19/30 G02F 1/13 CA (STN)

Claims (4)

(57) [Claims] 1. Formula I Wherein Hal is F or Cl and l is 1, 2 or 3
And r is 0 or 1 to 6, and E is -A-, -A
-CH ₂ CH ₂ - or -CH ₂ CH ₂ is -A-, A is trans-1,4-cyclohexylene, 1,4-phenylene, 3-fluoro-1,4-phenylene, 3,5-difluoro -1,4-phenylene or a single bond, and Q is -CF ₂ , -OCF ₂ , -CF ₂
CF ₂ —, —OCF ₂ CF ₂ — or a single bond, Y is H, F or Cl, and X and Z are each independently H or F). 2. Use of the phenylcyclohexanes of the formula I according to claim 1 as a component of a liquid-crystal medium for electro-optical displays. 3. A liquid crystal medium for an electro-optical display having at least two liquid crystal components, comprising at least one liquid crystal component.
A liquid crystal medium characterized in that the component is the phenylcyclohexane of the formula I according to claim 1. 4. An electro-optical display based on a liquid crystal cell, characterized in that the liquid crystal cell contains the medium according to claim 3.